Human activities in coastline are known to have a number of negative impacts, both direct and indirect, on the natural environment, including coral reef ecosystems. Coral reef health is also affected by natural factors such as disease and tropical storms. However, the ability of coral ecosystems to cope with and recover from these natural factors can be limited by the impact of human activities.
The associated increase in runoff from roads and buildings has resulted in greater amounts of polluted water entering coastal ecosystems . Exploitation of coastal resources, particularly through fishing, increased dredging for marina facilities and boat access navigation, beach food and building materials has also increased the amount of pollution affecting coral habitats.
Tourism and Recreation is by far the fastest-growing sector of the coastal economy. Coral reefs, especially, have significant recreative activity in coral reefs include snorkeling, diving, navigation and fishing. Increasing tourism will also affect overall coastal development and population.
Coastal pollution; Sediments, fertilizers and other nutrients. For example, sediment, sticking out of the water can suffocate corals and cover the habitat necessary for coral growth. In addition, turbidity in the water column reduces the availability of light for coral growth.
Nutrient pollution can promote increased growth of algae and bacteria, kill seaweeds and corals, and impair fish growth and reproduction. Other pollutants such as heavy metals and petroleum are also harmful.The effects of coastal pollution can make coral ecosystems more vulnerable to other stressors.
Climate change and diseases. fishing and overfishing; Coral habitats are very diverse and support is important commercial and recreational fisheries, and the pharmaceutical industry.
Impacts of fishing include: (1) over-exploitation of fish, invertebrates and algae for food and the aquarium trade; (2) almost total loss of a single species or a group of species (3) bycatch of non-target species.
Spilling fuel, chemicals, or cargo causes an additional damage.
Marine debris: Marine debris adversely affects marine life through the destruction of essential habitats, entrapment and uptake by marine organisms and seabirds. The most notable impacts of marine debris on coral reef ecosystems come from abandoned fishing gear, including fishing equipment Synthetic net and fishing line, in use since the 1950s, can survive in the ocean for decades and be transported thousands of miles by ocean currents and wind.
The lost fishing gear consisted of conglomerations of nets and line spools through reef habitats, crushing coral, expelling sessile organisms, snagging on coral, and entrapment of marine life.
Oil spills; Recovery from oil spills in shallow water can take a coral reef ecosystems decades.
Cable Laying Works; The need for submarine cables, especially fiber optic cables, to support the telecommunications industry has been increasing rapidly. The installation of ropes and cables for unprotected handling operations has been found to disturb and destabilize benthic structures.
Higher levels of carbon dioxide coral growth rates have been linked to declines. Reduced growth rates can affect coral reefs’ ability to track rising sea levels or recover from natural disturbances such as hurricanes and volcanoes.
In addition, high sea surface water temperatures cause corals to bleach due to the loss of beneficial algae from coral tissues. Although corals can recover from brief episodes of bleaching, corals become bleached and then die when water temperatures get too hot and stay high for long periods of time.
Diseases; Since the mid-1980s, the incidence of diseases affecting marine plants and animals has increased.
Tropical Storms The extent of coral ecosystem damage from tropical storms is influenced by reef physical structure and biological composition, and the path, strength,and duration of a storm. Storms can generate high storm surges, heavy rainfall, and very strong winds, causing physical and water quality-related damage to coral reefs.
Trade; Many coral reef species are collected at the national and international level to provide growing demandforsafood, aquarium animals, live fish food, building materials, jewelry, pharmaceuticals, traditional medicines and other products. Harvesting at unsustainable levels can lead to reductions in abundance and size of important species, shifts in species composition, and, in some cases, population explosions of other organisms.
Some of the techniques used to harvest organisms from coral reefs, such as poisoning fish with as cyanide and destroying coral colonies, are also very destructive.
Rising population densities and associated coastal development as well as increased fishing, agricultural, and industrial activities are the major causes of pressures as well.
Coral reefs vary widely in their ability to withstand pressure and recover from damage or disturbance. This may be partly driven by ecological factors, including the species composition of the reef itself and its connectivity to other reefs. In addition, the physical setting of a reef (distance from land, reef depth, and the rate of water flow in the area) influences its vulnerability.
Extensive construction and development for housing, roads, ports, and other development have been required to support both the residential and tourist populations. Poorly managed coastal development puts stress on coral reefs through direct damage from dredging, land reclamation, and sand and limestone mining for construction as well as through less direct pressures such as runoff from construction sites and removal of coastal habitat.
The loss of mangroves and seagrass, which filter sediment and nutrients coming from the land, has been widespread. Increased sediment incoastal waters reduce the amount of light reaching thecorals and hinder the ability of their symbiotic algae(zooxanthellae) to photosynthesize.13In addition, the widespread discharge of untreatedsewage is a major source of nutrients entering coastalwaters.
Coral reefs flourish in waters nearly devoid of nutrients, and increased nutrient concentrations promote algal growth at the expense of corals. Characterizing the pressures acting on any reef is complex, as there are multiple sources of stress operating over several spatial and temporal scales. However, it is necessary in order to be able to protect them.